Hi AXmonster,
the Thermos was to keep the coolant warm overnight to make the cold start less cold. I didn't store the coolant directly in the Thermos but rather ran it through a copper tubing coil in the bottle, thus heating the water in the bottle. In the morning a windshield wiper pump circulated the then-cold coolant through the bottle with then-lukewarm (ca. 40 C) water, bringing a coolant temperature rise of about 5 C after about 5 min of pumping. Not very effective.
Why it didn't work that well:
> Bottle capacity too small
> Indirect system: didn't store coolant directly because I was too chicken to have the Thermos at coolant system pressure (1 bar = 15 psi); as it was I had 8 additional hose clamps in the system! With direct storage you could pump the warm coolant out and lock the cold stuff in the Thermos until the engine is warm, then gradually pulsing it back into the system.
> Hoses remained filled with coolant --> convective cooling all night long. That's why the bottle only had 40 C in the morning vs. 68 C without hoses or coil (operating temp. is 90 C).
BTW there's a commercial system like this available (
www.waermespeicher.com), but it's bulky and expensive.